The present invention relates to a steam trap for draining off condensate from a collecting chamber in which condensate resulting in a pressure gas system is collected, the collecting chamber being pressurized by a gas pressure which, depending upon the operating state of the pressure gas system, may be a negative pressure below the atmospheric pressure, an overpressure above the atmospheric pressure or an atmospheric pressure itself, with the steam trap comprising the following components:
a level indicator being designed for indicating the level of filling of condensate within the collecting chamber, in particular when a maximal level of filling is reached or exceeded within the collecting chamber,
an outlet valve which is associated with the collecting chamber and designed for draining off condensate from the collecting chamber, in particular against the atmospheric pressure,
an electronic unit which evaluates the signal emitted by the level indicator and activates the outlet valve when the maximal filling level in the collecting chamber is reached or exceeded,
a housing with a compressed-air connection (24) for the connection with the pressure gas system and an outlet.
Condensate is usually generated in compressed-air systems which, apart from water, may also contain oil. The oil essentially arises in compressors where it is used as a lubricant. For this reason, the condensate in the compressed-air systems has an adverse effect, it is, as a general rule, very aggressive and must therefore be collected and drained off from time to time from the pressure gas system which is a closed pressure gas system per se. In doing so, the loss of gas or of compressed air is to be kept as low as possible. This task is solved by generic steam traps.
Consequently, steam traps consist essentially of a unit for the indication of at least one level (the “level indicator”) in a condensate collecting chamber and of a valve. Depending upon the indicated level, the valve is activated by means of a mechanical or an electro-mechanical device. By means of the gas pressure existing in the collecting chamber, the condensate is discharged from the compressed-air system via the valve.
A regular maintenance of these devices is required because wear and tear and contamination impair their function after a prolonged operating time. As a general rule, maintenance is, however, restricted to the mechanical part of the steam trap whereas the part which contains the electric control requires no maintenance.
Such a steam trap is known for instance from EP 0 391 250 B1. The same describes a device for the draining-off of condensate from compressed-air systems or the like, with a collecting chamber for condensate permanently coupled to the compressed-air system and with a diaphragm valve sealing the outlet of the collecting chamber, with two sensors for recording and indicating two capacitive, different filling levels and controlling the diaphragm valve via an electronic unit and a control valve being arranged within the collecting chamber. The sensors are arranged in a vertical distance from each other in a tube which vertically projects into the collecting chamber and which is closed at its outer end, and they are electrically connected with the control valve. All the components mentioned are accommodated within one housing, and they are connected with each other by means of conventional fastening and connecting devices. A disadvantage of the steam trap described above is that the same must, as a general rule, be disconnected from the electric power supply for maintenance work. This always requires a trained electrician or an expert in the field of electrical engineering unless the device is connected to the power supply and/or to a control unit by means of costly electric plugs which can also be handled by non-experts. Such plug-and-socket connectors are expensive, and their wiring is a difficult operation. As far as the maintenance of the mechanical parts is concerned, no electrician or expert in the field of electrical engineering is required. After the removal from the compressed-air system, the devices must then be disassembled in order to maintain and/or repair moving parts and gaskets. Furthermore, the collecting chamber and the sensors are to be cleaned. Prior to the re-start of operation, a function and pressure test is required. This makes maintenance work time-consuming, and the possibility of a faulty assembly exists.
Maintenance is required on a regular basis and entails a rather high expenditure. The expenses essentially depend upon the fact that the replacement of individual components is time-consuming and expensive. Another disadvantage is that during maintenance work the steam trap has to be disconnected from the pressurized system for a comparatively long period of time.